High-resolution three-dimensional variable-density groundwater flow and coupled salt transport models (abbreviated 3D-VD-FT models) are useful instruments to support coastal groundwater management strategies and to forecast impacts of climate change. However, the ability of 3D-VD-FT models to provide accurate groundwater salinity predictions depends on computational capabilities, availability of sufficient and adequate (high-resolution) data and understanding of groundwater salinity processes in the subsurface. Often, for instance, local aquifer heterogeneities are simplified in numerical models. In doing so, flow and transport are simplified, and consequently, local groundwater salinity changes become difficult to predict accurately. New avenues in data acquisition and computational methods have opened up the possibility to greatly improve the accuracy of predictions. Recent developments in innovative geophysical monitoring methods are able to observe salinity and (indirect) flow velocities in detail. For instance, one can use automated measurements with Electrical Resistivity Tomography (abbreviated ERT) to intensively monitor salinity changes, and one can use measurements with Active Heating-Distributed Temperature Sensing (abbreviated AH-DTS) to monitor groundwater flow velocities. In this research, we are examining to what extent the predictive capacity of 3D-VD-FT models can be improved when 3D-VD-FT models are integrated with data from ERT and AH-DTS measurements. To achieve this, we are developing a high-resolution 3D-VD-FT model calibrated with data from a scavenger well field study called the FRESHMAN pilot, located in Scheveningen, a district of the city The Hague, the Netherlands. Moreover, we are assessing the ability of the 3D-VD-FT model to reproduce observed groundwater salinity changes during multi-level groundwater extractions and impact of these extractions on upconing and downconing of fresh, brackish and saline groundwater. The FRESHMAN pilot allows for a unique view in the subsurface during groundwater extractions due to intensive monitoring by incorporating conventional hydrogeological monitoring methods and innovative geophysical monitoring techniques.